Gen~ issue with some numbers related to buffer size

Messing around trying to make an envelope follower for some aplitude based trigger of processes, and while building it I ran into an issue that I couldn't figure out.
History reset(0);
count = accum(1);
out1 = count % 64;
out2 = count % 63;
The first outlet, does not report correctly in the scope~ and number~ objects, yet the second does. I am assuming this is related to being an integer multiple of the buffer size, but want to confirm that.
The reason this was an issue, is I am adding to a buffer to do an average over 64 samples , and I was failing the check to see if I had reached the last value, in order to reset the accum. Is it best practice to avoid these types of numbers? I figured it would make my math a bit familiar and easier to work with.